Data on family structure are drawn from the Gallup World Poll. The Gallup World Poll is conducted in over 140 countries around the world based on a common questionnaire, translated into the predominant languages of each country. With few exceptions, all samples are probability based and nationally representative of the resident population aged 15 years and over in the entire country, including rural areas. While this ensures a high degree of comparability across countries, results may be affected by sampling and non-sampling error. Sample sizes vary between around 1 000 and 4 000, depending on the country. The categories are self-assessed by the respondent.